"Half an eye" just shows ignorance to the origin of the eye. It evolved from nothing but a nerve cell to becoming more delicate and more complicated in perceiving information because the animals with better adapted sensory perception survived better.

But here's another thing human beings have witnessed. There were peppered moths in some forest in england that were all off white because that was the color of the bark of trees that grew there. Then factories came in an turned it all the tree bark ashblack and the few peppered moths with a mutated gene that made them darker began to survive better than the white ones. Now, there are still peppered moths that occasionally appear lighter than the others, and for now their destiny is to get snagged by birds but the gene will keep mutating.